1. Field of the Invention
The present invention relates to air supplying apparatus which condition air in terms of cleanliness, temperature and humidity and which supply the controlled (conditioned) air into a room.
2. Description of Related Art
Air supplying apparatus are used for the purpose of supplying clean air, or clean air with controlled temperature and humidity into rooms which are in need of such conditioned air. Rooms requiring conditioned air include, e.g., rooms in which semiconductors, electronic devices and precision devices are produced, rooms in which pharmaceutical products or foodstuffs are produced, hospital operating rooms, and so forth. (Such rooms will be generally referred to as "clean rooms", hereafter.)
An air cleaning system, which is one type of such air supplying apparatus, has an air recirculating blower and a filter which are disposed outside a room, and air supply pipes installed in the ceiling wall and side walls of the room. The supply pipes have outlet openings which open in the surfaces of such walls, so that filtered air blown by the blower is supplied into the room through the outlet openings.
This type of system can supply air over a wide area in the room at a sufficiently large flow rate, but requires much cost and labor to install the air supply pipes, which must be embedded in the ceiling and side walls of the room and which open through the inner surfaces of the ceiling and side walls. In particular, introduction of this system to a room of an existing building requires a long construction period, as well as a huge cost.
An air cleaning unit has been known in which an air recirculating blower and a filter are assembled together in a casing which is provided at its top and bottom ends with a clean air discharge opening and a room air suction opening respectively. It is possible to clean the air in a room with such an air cleaning unit. This unit, however, can supply clean air only to limited portions of the room, and is unable to recirculate air at a sufficiently large rate to clean an entire room. With such air cleaning units, therefore, it is not possible to clean the air in a room to a desired extent.
In order to overcome these problems, Japanese Laid-Open Patent No. 59-44538 proposes an improved air cleaning unit which employs a columnar structure equipped with an air suction opening and an air recirculating blower. A duct of a specific cross-sectional shape is provided on the upper side of this columnar structure so as to extend along the lower surface of a ceiling. Air outlets are provided in the duct. A plurality of such air cleaning units are used in a room having a large volume. In this known air cleaning unit, however, no specific consideration has been given to the pattern of distribution of the air discharged from the air outlets. Consequently, the cleaned air cannot be supplied uniformly over the entire area of the room, which undesirably results in local concentrations or thinning of the controlled air, causing the cleanliness of the air in the room to be locally degraded, or the temperature and/or humidity to be deviated from the target level at local regions in the room.
This type of air cleaning unit also poses a problem in that a considerably high level of noise is generated during its operation from, for example, the motor and blades of the blower. Consequently, noise limits are often exceeded in rooms where silence must be kept, e.g., hospital operating rooms. This problem is serious particularly when a plurality of such air cleaning units are used to cover a large space in a large room having a large internal volume.